Appendix TL 789 clay ironstone being (according to Bloxam) for every ton of iron smelted— , ~ . . , ^ 0 i Calcined Ore...... 4$ c\vt Grey Cast Iron < Coal .......... 50 ( Limestone ... ... 17 ( Calcined Ore \ Hematite... \Vhite. Cast Iron X Forge Slag Coal ( Limestone 28 10 10 42 14 and one-third more air is supplied in the second case. Hematite is a very pure red ore containing some 70% of iron, while the above-mentioned ore will never have more than 50%, JP. 74. Cast Iron (Effect of Elements). Carbon exercises the greatest change in cast iron, and its effects have been well explained. Silicon, after carbon, is the most useful element. If present up to 3!% it produces soft, strong, grey iron ; and if added to a hard, whitish, and cheap iron, it will make it strong and grey. It is now much used to improve poor irons, but should only be present in small quantities in iron that is to be chilled. Sulphur is prejudicial, causing blowholes : it should not exceed '15 %. Phosphorus is also harmful, for though giving fluidity, it pro- duces brittlen ess if in excess of i%. Manganese tends to dissolve the graphite and promote com- bined carbon, and confers the property of chilling. If more than i% it causes large crystals as in Spiegeleisen. Rapid solidifica- tion also favours combined carbon (see Chilling, p. 34); The following foundry irons are the mean of many good specimens : WOOLWICH, 1858, * Graphite. Si. P. S. Mn. Percentages 2*59 i '42 '39 •06 *5* .